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As the carrier in the flotation process, bubble motion features have a significant impact on the flotation efficiency. The regulation of bubble characteristics is an effective method to enhance the flotation process. In recent years, microbubble flotation has received extensive attention. This paper reviews the advance of microbubble flotation from microbubble generation, microbubble features regulation and mineralization mechanism. The foaming principles and applications of jet foaming, microporous medium foaming, dissolved gas foaming, ultrasound foaming and electrolysis foaming are introduced. The regulation mechanism of microbubble size is analyzed from surfactants, electrolytes and energy input. The regulation mechanism of microbubble movement characteristics is discussed based on the bubble shape and rising velocity. Interaction mechanism of particles and microbubbles is fully analyzed from particle-bubble collision, attachment and detachment. Finally, the development of microbubble regulation and action mechanism is prospected.

By means of multi-field coupling numerical simulation and field measurement, the pressure relief effect and burst elimination range of side coal gas in goaf caused by inclined coal mining are analyzed. Taking the inclined longwall working face of Hongyan Coal Mine as the research object, a fluid-structure coupling model considering elastic-plastic damage was established to simulate the displacement and failure of surrounding rock after mining, and the changes of lateral stress concentration coefficient and permeability in goaf were analyzed. The gas pressure in the range of 10 m to 23 m in the goaf side was monitored and compared with the simulation results. The simulation results show that fracture penetration, stress concentration and initial elastic zone will form on one side of goaf after mining, and the gas pressure in fracture penetration zone can be effectively released. The field monitoring results show that the gas pressure decreases gradually with the advance of working face. It is found that the numerical simulation results are of guiding significance to predict the scope of gas outburst zone, and the elimination range of the inclined longwall working face of Hongyan Coal Mine is determined to be 10 m.

Flotation process is a multi‐phase and multi‐scale complex flow system, in which hydrodynamics plays an indispensable role. In recent years, computational fluid dynamics (CFD) numerical simulation has gradually become a powerful tool for studying flotation. In this review, the theories of CFD numerical simulation in flotation research were reviewed, involving various turbulence models and multi‐phase flow simulation approaches. An attempt has been made to analyze and discuss the characteristics and applicability of different turbulence models and multi‐phase flow simulation approaches in flotation researches in detail. The CFD simulation of two commonly used flotation devices, that is, mechanically agitated flotation machine and flotation column, has been reviewed in detail. The detailed principles, operation, and hydrodynamic of flotation devices were discussed from the viewpoint of CFD. The advances made in CFD simulation for studying flotation process, including particle suspension, bubble dispersion, particle–bubble collision, attachment, and detachment subprocesses have been critically analyzed. Focused analysis was given on the influence mechanism of turbulence on the particle–bubble interactions. Finally, the gaps in the available literature are discussed and potential research directions are also proposed. [ABSTRACT FROM AUTHOR]